The present invention relates to a lateral type MOS transistor for withstanding a high voltage.
A lateral MOS transistor comprises a source region, a channel region and a drain region, arranged respectively in the top portion of a semiconductor substrate. In the device current flows in the channel region between the source and drain regions which are naturally formed with curved portions where breakdown is likely to occur with somewhat low breakdown voltage. Prior to the invention some attempts have been carried out in order to obtain high breakdown voltage. However, in these attempts, new processes must be added to an ordinary fabricating process.